1. Field of the Invention
The present invention relates generally to a recording medium library apparatus. More particularly, the invention relates to a magnetic tape library apparatus having magnetic tape cartridge entry and ejection units.
2. Description of the Related Art
Magnetic tape units are one of diverse kinds of external storage devices for use with computers. The magnetic tape units operate most commonly on what is known as the open reel system using 0.5-inch wide tapes. The chores of manually loading the open reels have been alleviated by widening acceptance of automatic tape loading devices. Today, operators' burdens are further alleviated by the widespread use of magnetic tape cartridges. A magnetic tape cartridge, accommodating a tape having the same width as that of open reel tapes, allows the tape to be threaded out of the reel within for automatic tape loading.
A plurality of magnetic tape cartridges needed are entered in the magnetic tape library apparatus. Any one of the cartridges is selected and loaded to a magnetic tape drive unit for data recording and reproduction. The magnetic tape library apparatus comprises a cell unit having a plurality of cells each, accommodating a magnetic tape cartridge; a magnetic tape drive unit for recording and reproducing data; and an accessor for automatically switching magnetic tape cartridges between cell unit and magnetic tape drive unit. The magnetic tape library apparatus further comprises a cartridge entry unit for entering magnetic tape cartridge into the library apparatus and an automatic cartridge ejection unit for automatically ejecting magnetic tape cartridges from inside the library apparatus. Magnetic tape library apparatuses of this kind are widely used as an external mass storage device for computers. These apparatuses are required to operate unfailingly when unattended.
Cartridge entry units proposed so far have failed to give sufficient consideration to the relations between the disposition of the accessor and the structure of the cartridge entry unit. That is, each magnetic tape cartridge entered into the conventional cartridge entry unit is rotated 90 or 180 degrees by a rotation mechanism therein for delivery to the accessor. This necessitates a complicated structure of the cartridge entry unit, which in turn requires enlarging the library apparatus in scale. In addition, it takes time for the rotation mechanism to rotate the entered magnetic tape cartridge. That means more time required for cartridge entry processing.
The typical prior art automatic cartridge ejection unit comprises a pair of catch arms rotatably attached at one end thereof to shafts, a plurality of feed rollers attached rotatably to the catch arms, and a tray assembly for carrying the cartridge released by the catch arms. The tips of the catch arms have guide members that allow the catch arms to catch the cartridge horizontally. One disadvantage of this prior art structure is that cartridges cannot be transported stably inside the apparatus because it is difficult for the catch arms to grip each cartridge with a uniform force. Another disadvantage is that the catch mechanism tends to be large in scale because each catch arm is supported rotatably by its corresponding shaft.